This msg has been posted in the scripts forum as well:
<http://www.adobeforums.com/cgi-bin/webx/.3bbf2765.3bc473be>

My intention is to have only the lowest and the highest values for the combined RGB channels (RGB composite) adjusted by a script.

Description:
Like many I've got a bunch of digital images I need to edit. Often images have somewhat a greyish 'veil'. This can easily be corrected in Photoshop using the levels adjustments manually.
With 1000's of images this can become rather cumbersome, so I am looking for a script that would do that.
Photoshop provides the 'auto'-Levels function that can easily be inserted into an 'action' that runs over the selected files.

But the Auto-function applies adjustments to all values for each RGB channel separately resulting in a change of the greypoint
This is NOT pursued.

Below please find detailed description:

Photoshop Script for adjusting the combined RGB levels in a given file (TIF or PSD)

Goal:

Creating a script that is able to read the current RGB Input Levels (0 255) and write newly calculated values into the corresponding Input Levels.

The Auto-function applies the adjustment of all these values for each RGB channel separately resulting in a change of the greypoint

This is NOT pursued.

Only the 2 values for the combined RGB channels shall be adjusted by the script.

Script / Action Details:

1.Open a TIF or PSD File
2.Insert a new adjustment layer for levels
3.In levels, find the lowest value Vx (left) and the highest value Vy (right) form a given image
4.add a user defined value (for example 2) to the value left (Vx +2)
5.subtract the same user defined value from the value right (Vy-2).
6.write the newly calculated values into the corresponding fields of Input Levels.
7.ok
8.select the background level
9.save file
10.close file

I am certain this is possible by means of a script or something and hope you might have a solution for that.

I am looking forward to receiving your feedback, suggestions or even the solution itself. With kind regards,
Hans Loepfe

Hans_Loepfe

Replied in the following topics

Script for adjusting levels in RGB composite only